The League of Conservation Voters will spend a record $25 million this cycle, organizers announced Thursday, five times what the environmental group spent on the 2010 midterms.

“We are poised to spend by far the most money we have ever spent in an election cycle,” President Gene Karpinski said in a conference call with reporters.

Most of the money, approximately $20 million, will be targeted to help Democrats running for Senate in Colorado, Iowa, Michigan and New Hampshire. The league’s Alaska affiliate is also backing incumbent Democrat Mark Begich there. Another $5 million will go to assist pro-environment gubernatorial and legislative candidates in tandem with the league's state affiliates. The stakes are high for environmental organizations facing a possible GOP takeover of the Senate. Republicans must pick up a net of six seats in the midterms to win the majority.

Karpinski pointed to a long list of bills opposed by the league in this Congress that cleared the House but were blocked by the Democratic-controlled Senate. Senate Minority Leader Mitch McConnell of Kentucky “has made it clear that if he is the Majority Leader, one of his top priorities is blocking the EPA from enforcing the Clean Air Act” to curb carbon pollution, Karpinski warned.

The league will also back pro-environment Republicans, he added, including Sen. Susan Collins, of Maine, and other GOP endorsements yet to be announced. But most of the league’s targets so far are Republicans. Also today, the league released a TV ad attacking Republican Joni Ernst, running against Democratic Rep. Bruce Braley for Iowa’s open Senate seat. The ad is part of a $1 million joint campaign to defeat Ernst that the league announced in June with the Sierra Club and the Environmental Defense Action Fund.

Environmental organizations, including the new NextGen Climate Action Committee super PAC launched by hedge fund manager Tom Steyer, have emerged as a significant counter-weight to the unrestricted spending by conservative organizations backed by the billionaire industrialists Charles and David Koch.

The League of Conservation Voters is among the top 10 outside spenders in this midterm, according to the Center for Responsive Politics.

A big focus for the league in this election will be a voter turnout and mobilization campaign targeting so-called drop-off voters that tend to show up for presidential but not midterm contests, including young, Latino and female voters. The league has also joined with other environmental groups in a “Give Green” fundraising campaign that has rounded up a record $4.5 million for candidates both in the form of direct PAC contributions and bundled campaign donations, Karpinski said.